// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_SPDY_SPDY_FRAME_BUILDER_H_
#define NET_SPDY_SPDY_FRAME_BUILDER_H_

#include <stddef.h>
#include <stdint.h>

#include <memory>
#include <string>

#include "base/strings/string_piece.h"
#include "base/sys_byteorder.h"
#include "net/base/net_export.h"
#include "net/spdy/spdy_bug_tracker.h"
#include "net/spdy/spdy_protocol.h"

namespace net {

class SpdyFramer;

// This class provides facilities for basic binary value packing
// into Spdy frames.
//
// The SpdyFrameBuilder supports appending primitive values (int, string, etc)
// to a frame instance.  The SpdyFrameBuilder grows its internal memory buffer
// dynamically to hold the sequence of primitive values.   The internal memory
// buffer is exposed as the "data" of the SpdyFrameBuilder.
class NET_EXPORT_PRIVATE SpdyFrameBuilder {
public:
    // Initializes a SpdyFrameBuilder with a buffer of given size
    SpdyFrameBuilder(size_t size, SpdyMajorVersion version);

    ~SpdyFrameBuilder();

    // Returns the total size of the SpdyFrameBuilder's data, which may include
    // multiple frames.
    size_t length() const { return offset_ + length_; }

    // Returns a writeable buffer of given size in bytes, to be appended to the
    // currently written frame. Does bounds checking on length but does not
    // increment the underlying iterator. To do so, consumers should subsequently
    // call Seek().
    // In general, consumers should use Write*() calls instead of this.
    // Returns NULL on failure.
    char* GetWritableBuffer(size_t length);

    // Seeks forward by the given number of bytes. Useful in conjunction with
    // GetWriteableBuffer() above.
    bool Seek(size_t length);

    // Populates this frame with a SPDY control frame header using
    // version-specific information from the |framer| and length information from
    // capacity_. The given type must be a control frame type.
    // Used only for SPDY versions <4.
    bool WriteControlFrameHeader(const SpdyFramer& framer,
        SpdyFrameType type,
        uint8_t flags);

    // Populates this frame with a SPDY data frame header using version-specific
    // information from the |framer| and length information from capacity_.
    bool WriteDataFrameHeader(const SpdyFramer& framer,
        SpdyStreamId stream_id,
        uint8_t flags);

    // Populates this frame with a SPDY4/HTTP2 frame prefix using
    // version-specific information from the |framer| and length information from
    // capacity_. The given type must be a control frame type.
    // Used only for SPDY versions >=4.
    bool BeginNewFrame(const SpdyFramer& framer,
        SpdyFrameType type,
        uint8_t flags,
        SpdyStreamId stream_id);

    // Takes the buffer from the SpdyFrameBuilder.
    SpdySerializedFrame take()
    {
        if (version_ == HTTP2) {
            SPDY_BUG_IF(SpdyConstants::GetFrameMaximumSize(version_) < length_)
                << "Frame length " << length_
                << " is longer than the maximum allowed length.";
        }
        SpdySerializedFrame rv(buffer_.release(), length(), true);
        capacity_ = 0;
        length_ = 0;
        offset_ = 0;
        return rv;
    }

    // Methods for adding to the payload.  These values are appended to the end
    // of the SpdyFrameBuilder payload. Note - binary integers are converted from
    // host to network form.
    bool WriteUInt8(uint8_t value) { return WriteBytes(&value, sizeof(value)); }
    bool WriteUInt16(uint16_t value)
    {
        value = base::HostToNet16(value);
        return WriteBytes(&value, sizeof(value));
    }
    bool WriteUInt24(uint32_t value)
    {
        value = base::HostToNet32(value);
        return WriteBytes(reinterpret_cast<char*>(&value) + 1,
            sizeof(value) - 1);
    }
    bool WriteUInt32(uint32_t value)
    {
        value = base::HostToNet32(value);
        return WriteBytes(&value, sizeof(value));
    }
    bool WriteUInt64(uint64_t value)
    {
        uint32_t upper = base::HostToNet32(static_cast<uint32_t>(value >> 32));
        uint32_t lower = base::HostToNet32(static_cast<uint32_t>(value));
        return (WriteBytes(&upper, sizeof(upper)) && WriteBytes(&lower, sizeof(lower)));
    }
    bool WriteStringPiece16(const base::StringPiece& value);
    bool WriteStringPiece32(const base::StringPiece& value);
    bool WriteBytes(const void* data, uint32_t data_len);

    // Update (in-place) the length field in the frame being built to reflect the
    // current actual length of bytes written to said frame through this builder.
    // The framer parameter is used to determine version-specific location and
    // size information of the length field to be written, and must be initialized
    // with the correct version for the frame being written.
    bool RewriteLength(const SpdyFramer& framer);

    // Update (in-place) the length field in the frame being built to reflect the
    // given length.
    // The framer parameter is used to determine version-specific location and
    // size information of the length field to be written, and must be initialized
    // with the correct version for the frame being written.
    bool OverwriteLength(const SpdyFramer& framer, size_t length);

    // Update (in-place) the flags field in the frame being built to reflect the
    // given flags value.
    // Used only for SPDY versions >=4.
    bool OverwriteFlags(const SpdyFramer& framer, uint8_t flags);

private:
    // Checks to make sure that there is an appropriate amount of space for a
    // write of given size, in bytes.
    bool CanWrite(size_t length) const;

    std::unique_ptr<char[]> buffer_;
    size_t capacity_; // Allocation size of payload, set by constructor.
    size_t length_; // Length of the latest frame in the buffer.
    size_t offset_; // Position at which the latest frame begins.

    const SpdyMajorVersion version_;
};

} // namespace net

#endif // NET_SPDY_SPDY_FRAME_BUILDER_H_
